Statistical Stability Effects in Concrete Failure

Using a uniaxial localization model, it is shown that parallel elasticrcstf!1int increases ductility, while an increase in support flexibility or length ofspecimen reduces ductility. Statistical macroscopic nonhomogeneity of the specimen ismodeled by a system of uniaxial parallel elements of random properties following thenormal distribution. The stability analysis and Monte Carlo simulations explain that insuch a system an increase of length or support flexibility reduces not only ductility butalso the strength of the system. The effect on strength depends on the number ofclements (width of specimen), which represents a new non-classical statistical sizeeffect, and on the standard deviation of peak stress values within the parallel system.Existence of an inflection point and the prolonged tail on the descending branch isexplained by the nonhomogeneity of the specimen, and the shape of the descendingbranch, along with the location of the inflection point, is obtained as a function ofmachine stiffness, parallel elastic restraint, and specimen length and width. REFERENCE: Bazant, Zdenek P., and Panula, Liisa, "Statistical Stability Effects inConcrete Failure," Journal of the Engineering Mechanics Division, ASCE, Vol. 104,No. EMS, Proc. Paper 14074, October, 1978, pp. 1195-1212IIIIIIIIIIIIIIIIIII